In general, a synchronous reluctance motor is such motor for generating a torque of a motor using a reluctance, which is broadly being used in compressors.
An end plate provided with a balance weight is coupled to both sides of a laminated core of the synchronous reluctance motor to prevent a rotor from being eccentric. When a compressor has a larger capacity, the weight of the balance weight is increased. As a result, aligning the laminated core and increasing the coupling force between the laminated core and the balance weight have been considered as important tasks for improving reliability of products.
FIG. 1 is a disassembled perspective view showing a rotor of a conventional synchronous reluctance motor, FIG. 2 is an assembled perspective view showing the rotor of the conventional synchronous reluctance motor, FIG. 3 is a plane view showing a laminated core in the rotor of the conventional synchronous reluctance motor, and FIG. 4 is a sectional view taken along the line I-I of FIG. 2.
As shown in those drawings, the rotor 10 of the conventional synchronous reluctance motor includes a laminated core 1 formed by laminating a plurality of silicon steel sheet 7, end plates 3 fixed to both sides of the laminated core 1, and a balance weight 2 formed on each end plate 3.
An axial hole 1a is formed in the center of the laminated core 1, and a key groove 1b is formed in an inner circumferential surface of the axial hole 1a. A barrier 8 is formed in each region equally divided by 90° on the basis of the center of the laminated core 1. The barrier 8 has a plurality of holes 8a. A rivet hole 1c is formed between two barriers 8.
An axial hole 3a is also formed in the center of each end plate 3, and a key groove 3b is formed in an inner circumferential surface of the axial hole 3a. 
Each rivet hole 3c is formed in a periphery of the axial hole 3a of the end plate 3 at a uniform interval to correspond to each rivet hole 1c of the laminated core 1.
A rivet 4 penetrates the rivet hole 1c of the laminated core 1, and one end 4b of the rivet 4 is inserted into the rivet hole 3c of the end plate 3. The one end 4b of the rivet 4 is thereafter riveted. Therefore, the two end plates 3 are coupled to both sides of the laminated core 1 by the rivet 4.
A procedure for assembling such constructed rotor of the conventional synchronous reluctance motor will now be explained.
The one end 4b of the rivet 4 is inserted into the rivet hole 3c of the lower end plate 3 of the two end plates. The one end 4b of the rivet 4 is then inserted into the rivet hole 1c of the laminated core 1, thereby laminating the plurality of silicon steel sheets 7.
Here, the silicon steel sheets 7 are laminated in a state that a gauge bar 20 having keys 21 at its outer circumferential surface is inserted into the axial hole 1a of the laminated core 1 so as to align the laminated core 1 on the straight line.
Next, the one end 4b of the rivet 4 is inserted into the rivet hole 3c of the upper end plate 3 and an end of the gauge bar 20 is coupled with a nut 22. As a result, the end plates 3 are closely adhered with both sides of the laminated core 1.
An air layer (not shown) positioned between the silicon steel sheets 7 is removed by coupling the nut 22 to the end of the gauge bar 20. Thereafter, the one end 4b of the rivet 4 is riveted. The nut 22 is unscrewed again to separate the gauge bar 20 from the axial holes 1a and 3a, and accordingly the rotor 10 is completely assembled.
However, in such constructed rotor of the conventional synchronous reluctance motor, key grooves are formed in the inner circumferential surfaces of the axial holes of the end plates and the laminated core should be formed to align the laminated core and the keys of the gauge bar should individually be fixed into the key grooves, which makes it more difficult to align the laminated core.
In addition, if an outer diameter of the rotor is increased to maximize an output of the synchronous reluctance motor, the weight of the balance weight is also increased in order to improve the coupling force between the laminated core and the balance weight. However, in the rotor of the conventional synchronous reluctance motor, the laminated core and the balance weight are coupled to each other only using the rivet and the rivet hole is positioned in the periphery of the axial hole. As a result, the coupling force is maintained by the one end and the head of the rivet, which results in decrease of the coupling force therebetween.